1. Field of the Invention
The invention relates to mechanisms for adjusting the cutting height of a mower deck suspended from a driven vehicle.
2. Description of the Related Art
A first type of conventional mower deck height adjustment mechanism provides a lever arm that extends upwardly from the vehicle to be pivoted by one of the operator's hands. The lever is typically rigidly coupled with a laterally extending shaft that pivots about its own axis as the operator shifts the lever. The shaft is coupled with a linkage having a plurality of parts that act to raise and lower the deck as the shaft rotates while maintaining the deck in a generally level or horizontal position. A locking mechanism is provided for securing the lever, shaft or linkage in a particular position to fix the deck's operating height. The locking mechanism can be released by the operator so that the deck's height can again be adjusted.
This first type of height adjustment mechanism is relatively complex and requires the use of an undesirably large number of parts. Bushings or bearings are typically provided for pivotally supporting the shaft and the various pivoting linkage members. These bushings must be capable of withstanding relatively large force loads associated with the weight of the mower deck. Therefore many mowers provide bushings or bearings that are made of relatively high strength materials. These high strength bearings raise the cost of manufacturing and assembling the mechanism.
Many such height adjustment mechanisms must be grasped by one of the operator's hands while he simultaneously releases the locking mechanism with his other hand. Therefore the lifting operation may be difficult for the operator since he can only use one arm to shift the lever.
A second type of conventional mower deck height adjustment mechanism provides a lift arm carried by the vehicle between and beneath the operator's legs such that the operator can grasp and lift the lift arm with both hands while seated on the vehicle. The locking mechanism is often coupled with the lift arm such that the operator can release the locking mechanism while keeping both hands grasping the lift arm. The lifting operation is therefore accomplished more easily by the operator since he can use both hands and arms during lifting.
Many of the second type of lift mechanisms involve the use of a large number of parts and are therefore relatively complex. Also, pivot bushings or bearings made of relatively high strength materials are often utilized to pivotally support the various parts of the mechanism. Therefore these mechanisms are relatively costly to manufacture and assemble.
Mower decks that are carried by powered vehicles can become tilted out of a horizontal plane after periods of rough use. Mechanisms have therefore been provided for adjusting or correcting the attitude of the mower decks so that the deck can be returned to a level position. Leveling adjustment mechanisms often require several tools to be used simultaneously during the leveling operation. Many leveling mechanisms also require the operator to adjust the mechanism at a location beneath the vehicle that is difficult to reach. In addition, when these mechanisms are adjusted, the mower deck is often shifted out of correspondence with the height indicator gauges, such that the indicators no longer indicate the actual height at which the deck is cutting.
Therefore, it would be desirable to provide a mower deck lift mechanism that is simple in construction and requires the use of a relatively small number of parts. It would be desirable for a mechanism to allow adjustment of the mower deck height while maintaining the deck in level or horizontal position, and to allow the operator to lift the deck with both of his hands. It would be desirable to provide a mechanism with a leveling adjustment mechanism that allows the operator to return the deck to a level position. It would also be desirable for the operator to be able to make the leveling adjustment from an easily accessible location, and such that cutting height indicators remain accurate.